1. Field of the Invention
The present invention relates to methods and apparatus for cleaning deposits from a semiconductor wafer. More particularly, the present invention relates to methods and apparatus for chucking a wafer for cleaning deposited films and flakes from the edge and bevel portions of a semiconductor wafer.
2. Description of the Related Art
Semiconductor wafer fabrication involves a series of processes used to create semiconductor devices and integrated circuits (ICs) in and on a semiconductor wafer surface. Fabrication typically involves the basic operations of layering and patterning, together with others such as doping, and heat treatments. Layering is an operation used to add thin layers of material (typically insulator, semi-conductor or conductor) to the surface of the semiconductor wafer. Patterning is an operation that is used to remove specific portions of the top layer or layers on the wafer surface.
Once the integrated circuits on the wafer are completed, i.e., layering and patterning are implemented, the wafer is conventionally sliced into sections known as die. A large number of wafers are diced from a wafer, typically 100 to 1000. A wafer may comprise as many as 10 or more layers, each layer formed in a separate step. During processing of semiconductor wafers, films (i.e., layers) are deposited not only on the selected areas of the wafer surface designated for the die, but also on the margin of the wafer, i.e., the wafer edge and the bevel. The films may also be deposited on the backside of the wafer near the edge. These films located at or near the edge may become problematic during subsequent processing, such as occurring when the edge deposits begin to flake or peel off. This may result in contamination during subsequent process steps. For example, such flakes may cause a bridge between two conductors or prevent the formation of a pattern. The flaking may therefore cause processing defects which may result in die failure at test.
As integrated circuit devices grow smaller, higher conductance and lower capacitance is required of the interconnects. In order to accommodate these objectives, the trend has been towards the use of copper for interconnects and damascene methods for forming the interconnects in low-k dielectric materials. But fabrication processes that use copper interconnects require higher levels of cleanliness for the edge, beveled regions and back side of the wafer to prevent contamination of subsequent process steps.
One method for cleaning these deposits involves a spin processor, i.e., placing the wafer on a chuck and spinning the wafer at high speeds while selectively dispersing one or more chemicals over the wafer surface. But typically spin processors hold wafers at the wafer edge with tips that are nail like. With this method, any copper contamination located between the tips of the chuck and the wafer bevel or edge cannot be completely cleaned. Moreover, the tips of the chuck adversely influence the cleaning efforts directed to the backside off the wafer by disturbing the chemical flow.
Accordingly, it is desirable to provide a more effective method and apparatus for removing films from the bevel and edge of a wafer. Thus, what is needed is an improved wafer holder and method for holding a wafer during spin process cleaning.